This invention relates generally to solid state electronic timepieces with electrooptic displays, and more particularly relates to an improved circuit and display arrangement for indicating the hours and minutes in digital and "analog" fashion respectively.
Electronic solid state watches with electrooptic displays, such as light-emitting diode displays or liquid crystal displays have generally favored the presentation of the time in digits. One reason for this is that a digit can be presented with seven individually actuatable segments requiring seven leads between the display and the electronic circuit. Hours and minutes can be displayed using four digits. Examples of such timepieces are found in U.S. Pat. No. 3,863,436 -- Schwarzschild et al, issued Feb. 4, 1975 and in U.S. Pat. No. 3,953,964 -- Suppa et al, issued May 4, 1976, both assigned to the present assignee and exemplary of this type of watch.
On the other hand, when efforts have been made to display the hours and minutes on an electrooptic display in so-called "analog" fashion, i.e., representing the conventional hour hand and minute hand of a watch electronically, considerable technological difficulties are encountered. This is primarily due to the multiplicity of individual marker segments on the periphery of the display and the number of leads required, sixty in all, to display the minutes. Various efforts have been made to overcome this, as exemplified in U.S. Pat. No 3,922,847 -- Culley et al, issued Dec. 2, 1975 or U.S. Pat. No. 3,955,354 -- Kilby et al, issued May 11, 1976. The foregoing utilize concentric rings and use different color LEDs or sharing of the same markers for hours, minutes and seconds, respectively.
Other approaches to indicating minutes by radially disposed markers on an electrooptic display have employed techniques for dividing the minutes segments into groups and employing special switching techniques as exemplified in U.S. Pat. No. 3,987,617, issued Oct. 26, 1976 to A. Slob; U.S. Pat. No. 3,934,241, issued Jan. 20, 1976 to H. Weigert; and German Offenlegungsschrift No. 2,410,527 -- K. K. Suncrux Research Office.
Still other related approaches employ separate concentric rings of lights or markers as in U.S. Pat. No. 3,456,152 -- Andersen, issued July 15, 1969; U.S. Pat. No. 3,844,105 -- Kashio, issued Oct. 29, 1974; U.S. Pat. No. 3,258,906 -- Demby , issued July 5, 1966; U.S. Pat. No. 3,626,410 -- deKoster, issued Dec. 7, 1971 and Swiss Pat. No. 437,532 -- S.S.I.H. published Nov. 30, 1967. Assignee's U.S. Pat. No. 3,540,209 to Zatsky et al, issued Nov. 17, 1970 further illustrates a liquid crystal display for giving an "analog" time indication.
The basic problem with approaches in the prior at is that of circuit complexity and space requirements, as well as difficulty and expense involved in providing the many minute connections to the display.
Hybrid horological displays have been suggested which utilize both digits and radial markers for hours and minutes, respectively. An example is seen in applicant's U.S. Design Pat. No. D242,694, issued Dec. 14, 1976 in the names of Thompson and Sheffield. Improvements in reducing the complexity of the circuits for displaying minutes, as well as reducing the number of actuatable segments required, would greatly simplify solid state electronic watches.
Suggestions have been made for adding "ten seconds" indicators on a conventional hours and minutes digital watch as in U.S. Pat. No. 3,982,387 -- Tanaka, issued Sept. 28, 1976.
Accordingly, one object of the present invention is to provide an improved horological display utilizing a reduced number of segments in an electrooptic display.
Another object of the invention is to provide an improved display for indicating minutes by radially disposed markers and requiring fewer segments than in the prior art to indicate the passage of time from one minute to the next.
Another object of the invention is to provide an improved hybrid horological display and modulating/driving circuit for the display.